Planetary friction transmission



July 19,1932.

J. l1. HUNT PLANETARY FRICTION TRANSMISSION Filed Oct. 19, 1951 2 Sheets-Sheet l Jul 19,1932. H HUN r 1,868,234

PLANETARY FRICTION TRANSMISSION Filed 0017. '19. 1931 A 2 Sheets-Sheet 2 is immaterial for the Patented July 19, 1932 UNITED STATES PATENT OFFICE JOHN H. HUNT, OF DETROIT,'MIOIEI IGAN, ASSIGNOR GENERAL MOTORS CORPORATION, OILDETROIT, MICHIGAN, A CORPORATION OF DELAWARE Application filed October 19, 1931. Serial No. 569,781.

This invention relates to transmissions employing planetary motion of torque transm tting rollers where such rollers revolve on their own axes and-the latter revolve around the main axis of the transmission and where the axes of the rollers may lie at an angle to the main transmission axis or otherwise than par-' allel thereto.

Such transmissions will usually be of the variable speed planetary type in which friction rollers are interposed between coaxial discs provided with annular toric grooves in their opposed faces, the rollers being mounted in roller carriers which are themselves mounted in a roller cage.

In its simplest form, one of the coaxial toric discs or races may bethe. drivmg member and the other disc a stationary member whilst the driven member is the roller cage carrying the planetary rollers. In another form such as that shown in British Patent 343,988 there may be two sets of rollers in parallel forming a double toric transmission in which the end races may be connected to rotate with the input'shaft whilst a central race common to the two sets of planetary rollers may be held stationary, the driven shaft being connected to the roller cages. In any variable speed friction transmission of the toroidal type and whether planetary or otherwise, change of ratio is tilting each roller. axis in a plane passing through the center of the roller and containing the main transmission axis. The roller is tilted to a circle of contact of larger radius on one disc and of smaller radius on the other. This change of tilt and corresponding change of ratio may, through suitable controls for the rollers, be carried out directly or not- It may be the resultant motion from inclination (i. e. turning of the roller about an axis passing through the points of contact of the roller with the races) or from bodily displacement of the roller, all as hereinafter described. It purposes of the present invention just how the change of tilt is ef-' fected. I

In such a transmission, of the planetary type, the rollers have each a angular velocities about two axes at an angle effected by among the rollers, it is combination of I with each other when ever the-axes 0f the roll ers lie otherwise than parallel to the main transmission axis in planes containing the two axes of rotation.

Nowwhen a mass rotates with a combination of angular velocities about two axes at an angle with each other, a gyroscopic torque is developed. In the case of the rollers in the transmission, this gyroscopic torque tends to turn or tilt the rollers in the plane (i. e. about an axis normal to such plane passing through the center of the roller an containing the main transmission axis. This torque tends to tilt the roller, with slippage at the points of contact, and to change the ratio.

It can be shown that the gyroscopic torque to shift or to tend to has such a direction as shift the roller toward a higher ratio of output to input shaft speeds.

This torque or tilting couple may,-in actual practice at input shaft speeds of-3000 R. P. M. have a magnitude of more than twice that 'of the torque received and delivered as power by the roller itself. 7

These gyroscopic .forces must be resisted, eitherby the friction at the roller contact points involving, in the immediately foregoing instance, a pressure between rollers and races more than twice that required to transmit the power, or they must be resisted in some way through the control means, if they are not otherwise balanced. V

- Increased axial loadin to prevent the creep or tilt of a roller un er the influence of the 'gyroscopic torque is undesirable as in volving higher contact stresses and lower durability.

Furthermore,'if for any reason there is a variation in contact capacity or loading possible under the influence of the gyroscopic forces for the rollers to get out of ratio relatively to one'another with consequent destructive binding or slipping and loss of efficiency.

It should be noted that even if there were no gyroscopic or centrifugal forces tending to changethe ratio of a variable speed friction transmlssion, it would still be possible for the rollers to tilt out of another as a result of variations in say' conratio relatively to one tact capacity or loading unless the rollers,

' yield effecting tilt by inclinatmm'bodilydisplacement, or m any other way.

It .is not, however, always convenient or commercially expedient to build a friction transmission in which no yield of the roller support with bodily displacement or inclinatron and consequent tilt with resultant change of'ratio of any roller relatively to the others is ible. v v

' or these and other reasons there is considerable" advantage in designing the mecha I nism in such a way that an overloaded roller automatically changes its tilt very slightly in a direction corresponding to a ratio Egsltion in which it carries a smaller load.

0 load through the rollers of such a transmission is thus equalized. l

I 7 Whether the transmission is equalized or hon-equalized it .is very desirable that where planetary operation is involved, some means, other than a resistance through in creased axial loading or throughjthe control means should be employed to prevent change of tilt and ratio under the influence of the .gyroecopic torque, and other .forces peculiar to planetary operation.

- The neutralization of the gyroscopic torque is very desirable in the equalized t in or- ,der' thatequalization shall not be nterfered with and since the strength and especially.

the construction of ,the partsin equalized on is not otherwise capable of ab- *sorbing around ea h roller an or resisting the gyroscopic torque. In addition to the gyroscopic torque there is a centrifugal torque due to the unequal radial disposition o the roller about the transmimion shaft axis, for all angular positions of the roller other than those in which the roller/axis is either normal to the trans mission shaft axis or parallel thereto. This centrifugal torque is reversed as the roller axis is tilted from one side to the other of the normal to the transmission shaft axis v but is in the same direction as the gyroscopic torque for roller positions giving drive ratios of output to input greater than one to two.

The object of the. invention is to provide means for counterbalancing' or neutralizing these gyroscopic and centrifugal torques of which the gyroscopic torque is the principal one and to do this by incorporating a second wheelof-suitable mass and moment of inertia in the reverse directiontothe roller. a

The wheel may or may not have the same angular velocity as the roller; There is some advantage in rotating a wheel-with a smaller.

I I moment of inertia at a highei; speed.

So far as the gyroscopic forces are concerned the-wheel may mounted either on the outer end of the roller axis or on the inner end although from space considerations grouped on the inside of the roller, there will be a resultant centrifugal torque op the centrifugal torque on the roller or a roller positions giving drive ratiosof output to lnput other than one to two.

' There is thus a. further advantage in mounting the balance wheel on the outer end'bf the roller axis since otherwise its additidnal mass would have to be counterbalanced by .a mass of still larger centrifugal moment on the outside of the roller if the cam trifugal torque on the roller-is not to be ac- I tually augmented The accompanylng drawings show the application of the invention to a single toric 'planetary variablespeed friction transmission in which chan e .tilt induced by rollers accompanied by restoration and in which equalization between the rollers is automatically e'flected. This embodiment has 5 been chosen for purposes of example only and it will be understood that the. invention is applicable to any transmission employing planetary motion of torque transmitting rollers where such rollers revolve on their own axes and the-latter revolve around the main axis of the transmission and where the axes of the rollers may lie at an angle to the main transmision axis or otherwise than parallel thereto. v In the drawings:

Fi re 1 is a longitudinal central sec- I 13101) n a yertical plane of a single toric lanetary friction trans mission embodying t e invention. i

Figure 2-is 'a cross sectiontaken about on line 2-2 of Fi 1' showing themounting of the rollers withtheir balance wheels.

Figure 31's an enlarged cross sectional view of .ratio is effected by ly displacement of the I of one ofthe rockers in whichthe trunnion blocks for the roller carriers. are mounted.

Figure 4 is a detail part sectional view (.taken'alioutonline 4-4., of Fig. 2) 'showing one of the-roller carriers in which the rollers are mounted and the trunnion blocks on which the carriers are'journaled to permit the carriers with the rollers to rock on axes at an angle to,the axes on which the roll ers rotate. A convenient way of mounting.

the roller carrier withits tilting axis inclined to the plane in which the roller revolvesin.

planetary fashion around the axis of thedists Fig. 5 is an enlarged view of a roller and balance wheel taken'about a line 55 of Fig. 2 showing the mounting thereof and the manner in which the balance wheel is driven from the roller in an opposite direction thereto.

The driving disc 6, splined or slidably keyed on the driving shaft 7 is provided with a. torus groove8. The fixed stationary-disc 9 is provided with a similar torus groove 10. Between the discs 6 and 9 are three transmission rollers 11, 12, 13, spaced 120 apart as in Fig. 2. The parts are pressed together to maintain engagement by a spring 7a.

The spider or roller cage 14 is splined or slidably keyed to the driven shaft 15.

The rollers 11, 12, 13, are mounted in carriers 16, 17, 18. The spider or roller cage 14 has three arms 20 supporting an outer rin 21.

ivoted'at 22 on each arm is a rocker composed of a front plate 23 and arear plate 24, connected by webs 25. Recesses 26 in the side edges of the rockers receive the trunnions 27 of the trunnion blocks 28 which carry the s igots 19 for the roller carries. The axes of tile trunnions-27 are parallel to the axis of the transmission.

The roller carriers are thus supported ap- W proximately in the plane of the spider and between the arms thereof.

Balance wheels 16a, 17a, 180 316 mounted on the roller axes as shown in Figs. 1, 2, and 4, while Fig. 5 shows the method of mounting and the manner in which the wheel is driven from the roller in a reverse direction to the roller. I 1

Fingers 29 extend radially inward from the rocker plates .23 and are equipped with ball ends engaging recesses in a ring 30 loosely encircling shaft 7. A slight rotary movement of ring 30 will turn the fingers 29 and with them the rockers 23 in an opposite direction about their pivots 22 thus shifting theroller carriers and efl'ecting bodily displacement of the rollers from a position in which the roller axes intersect (i. e. are co-planar with) the axis of the discs into a position in which the axes are not co-planar. This is an unstable condition and the frictional forces acting on the roller will cause the roller. to incline i. e.

g to trace a spiral path on each disc) and the roller and carrier to turn i. e. tilt into a new ratio position on the carrier axis.

Assuming clockwise rotationof the driving shaft 7 and disc 6 (i. e. in the direction of the arrow on the shaft Fig. 1) a clockwise rotation of the ring 30 will result in'a counter-clockwise bodily displacement of the roller relatively to disc 6, with a resultant tilt of the roller on to a larger radius of disc 6 and a smaller radius of disc 9 equivalent to a higher speed of the roller cage relatively to the disc 6 i. e a higher gear ratio. 7

In order to effect a slight rotary movement of ring 30, the ring is connected to a drum shaped ring 32 by radial arms 31 and encircling this drumis a similar drum shaped ring 34 mounted on the ring 21 of roller cage 14. It will be seen that relative rotation of these two rings will result in the required relative rotation of ring 30 and bodily displacement of the rollers. The drum 34 is provided with cam edges 35 oblique to a radial plane and crossing the cam edges 33 of'drum 32 which lie substantially in or parallel to a radial plane. Bowls 36 cooperating with the cam edges are carried by arms 37 extending radi- 1 ally from a sleeve ring 38 and rotatable relatively to the shaft 7. The sleeve is slidable in either direction through a fork 39 operated by shift rod 40 constituting the ratio control rod. Thus, when sleeve 38 is moved to force preventing movement of the sleeve 38 to the left which then moves to the left and to a lower speed ratio under the influence of the frictional resistance opposing transmission of power. For positive change of ratio in either direction, the drums may be. provided with crossed camslots not shown.

The bodily displacement described above which results in the projected roller axis being moved. away from intersection of the disc or transmission axis is exactly theresult produced by inclination by which is meant the turning of the roller about an axis passing through the points of contact of the roller and the disc races from a position in which the projected roller axis intersects (i. e. is coplanar with) the disc or transmission axis.

Whenever the axes are not 'co-planar and rotation exists the rollers will continue to change ratio position. It follows therefore that for any desired ratio the axes must be restored to co-planar condition'just when the rollers begin to run on the race circles corresponding to the desired ratio. It is therefore necessary to provide some means whereby the normal motion of the parts in tilting cancels the bodily displacement or inclination which originated the tilting. This is achieved by arranging the axes of the roller carriers at an angle to the planes of the discs as illustrated in 4. When now the roller is displaced to a position in which its axis does not intersect the disc axis and the roller tilts into a new ratio position, the projected axis of the roller does not move in a plane parallel to the disc or transmission axis but due to the a'ngularity of the roller carrier axis is bound to move back to a position in which it intersects the transmission axis thereby reaching equilibrium in the new ratio.

position. The angularity ofthe roller carrier axis is so chosen that the roller axis will lntersect the transmission axis after tilting before the roller canleave the toric surfaces of the races with the maximum displacement which the control. mechanism can bring about.

In order to equalize the load' between the rollers so that each receivesand delivers an equal amount of power, it is necessary to per.- mit an. overloaded roller to receive the necessary bpdily displacement to reduce its load. This can only occur automatically if, as in the transmission herein described, the roller control is torque responsive and the resistance to speed changes proportional to the Y torque being transmitted. The necessary bodily displacement of an overloaded roller is "permitted and effected in the-following to turn slightly about its pin 22 without moving the adjacent rockers. I A part of the torque reaction of each roller is transmitted through the rockers 23 and.

. torque'transmitting roller and carrier therethe ball ends of the arms 29 to the ring 30.

e If all three arms'29 exert equal forces on the ring 30 the'ring receives only a turning couple which is resisted by an equal couple supplied through the arms 31 but if the load on one of the rollers is greater, there will alsobea force tending to move the. ring 30 radially in the direction of the vector A. The motion -will be practically parallel to the vector A, and will bepermitted through the flexibility of thedrum 32 withreference to forces a lied normal to the surface of the drum. 's radial motion will bring about equalization of the load by permitting a bodof the overloaded roller in a direction to cause it to tiltto a ratio angle I where it tends to drive the roller cage at a angle at a slig sli htly slower speed whilst the othe rockers w' be turned at the same time throu h small angles in the reverse direction with consebodilydisplacemerit and tilt to a ratio where they tend to drive the roller cage htly fastef'speed. In this way equalquent 1 ization is obtained by adding load to the remaining rollers as load is removed from the overloadedrollenv v I Referring now to Fig. 5, the carrier 18 is provided with a spi ot'41 constituting the physical axis aroun which theroller and balance wheel revolve. The roller 13 is mounted on a ball bearing 42. 'Fixedbn the ratio position. I

v spigot 41isasleeve 43 with radial arms 44 7 serving as a stationary cage for the balls 45 between the roller 13 and the balance wheel 18a. The sleeve43 is extended as shown to carry the ball bearing support 46 for the balance wheeL- The inner race of the ball bearing 42 is clamped between the roller carrier '18 andthe sleeve 43 by the c ap screw 47. 48 is a spring washer between the nut 49 screwed on the sleeve 43 and adjusted to give suflicient axial loadingand contact'pressure between ;the rollers 13 balls 45 and balance wheel 18a,

to transmit a drive from the roller 13 through the balls .45 to the balance wheel 18a.

It will be seen that since the cage for the balls 45 is held stationary'the balance wheel 13a will be driven in the-opposite direction torolle'r13.- a i As shown in the drawings, the balance wheel will be'given. a slightly higher speed than the roller since the driven diameter of the former is less than the driving diameter of the latter.

- The line 6-J3 indicates the median plane of the roller and the'masses grouped on the carrier on either side of this plane are so proportioned and-arranged 'thatthey will have aresultant centrifugal moment 0 posing and f counterbalancing the centrifugal torque tendin to tilt the'rolle'r whenever the roller is in ot er than the oneto two speed I claim: r 1. In atransmission gearing, a planetary for, the axis of said roller lying at an angle to the axis about which it has planetary motion, a balance wheel of such mass and moment of inertia capable of being rotated around the roller axis in an opposite direction .to the roller with such angular velocity that it will develop an opposing gyroscopic torque counterbalancing the gyroscopic torque tending to tilt the roller. in a plane passing through the center of the roller and containing the transmission axis.

.2. In .a transmission gearing, a planetary torque transmitting roller and carrier therefor, the axis of said roller lyin at an angle and otherwise than normal to t c, axis about which it has planetary motion, masses including the roller carrier and parts mounted thereon, proportioned and arranged so that the centrifugalmoment about the axis around which the roller tends to tilt of those portions of the said masses on that side'ofthe median plane of the roller more remote from Y the transmission axis is greater than the centrifugal moment. of those portions of'the said masses on that side of the roller nearer to the transmissionaxis by an amount such that the said masses will develop a resultant centrifugal torque opposing and counterbalancing the, centrifugal torque tending to tilt the roller in a plane passing through the center of the roller and mission axis. a

3. In combination a transmission gearing according to claim 1 in which the balance wheel forms part of the roller carrier masses on that side of the median plane of the roller more remote from the transmission axis, proportioned and arranged so that the centrifugal moment of the said masses aboutthe axis around which the roller tends to tilt isgreater than the centrifugal moment of the roller carrier masses on that side of the median plane of the roller nearer to the transmission axis by an amount such that the said masses will develop a resultant centrifugal torque opposing and counterbalancing the centrifugal torque tending to tilt the roller in a plane passing through the ,center of the roller and containing the transmission axis.

4. In combination, a transmission gearing according to claim 1 in which the speed ratio is variablebv changing the angle at which the axis of the roller lies to the axis about which' it has planetary motion and in which the balance wheel forms part of the roller carrier masses on that side of the median plane of the roller more remote from the containing the trans- .transmission axis, proportioned and arrangedso that the centrifugal moment of the said masses about the axis aroundwhich the roller tends to tilt is greater than the centrifugal moment of the roller carriermasses on that side of the median plane of the roller nearer to the transmission axis by an amount such that the said masses will develop a resultant centrifugal torque opposing and counterbalancing the centrifugal torque tending to tiltthe roller'in a plane passing through the center of the roller and containing the transmission axis.

5. In combination, a transm ssion gearing according toclalm 1' in which the roller is im terposed between coaxial torus discs in frictional torque transmitting contact therewith,

the speed ratio being variable (by tilting the roller on to a circle of contact of larger radius on one disc and lesser radius on the other disc and in which the balance wheel forms part of the roller carrier masses on that side of the median plane of the roller more remote from the transmission axis, proportioned" and arranged so that the centrifugal moment of the said masses about the axis around which the roller tends to tilt is greater than the centrifugal moment of the roller carri r-masses V on that side of the median plane of the'roller nearer to the transmission axis by an amount such that the said masses will develop a re- 1 sultant centrifugal torque opposing and counterbalancing the centrifugal torque tending to tilt the roller in a plane passing through the center of the roller and containing the transmission axis.

discs, I a plurality of planetary torque trans- 'mitting rollers with carriers and balance wheels therefor interposed between said discs, means holding the discs and the rollers in frictional torque transmitting contact, means for causing the torque reaction of the frictional forces acting on the roller to tilt the rollers and change the speed ratio, means whereby the load carried by each roller is automaticalely equalized by a resultant tilt from a'yielding displacement-of an overloaded roller, each balance wheel forming part of theroller carrier masses on that side of the median" plane of the roller more remote from the trans mission axis, proportioned and arranged so that the centrifugal moment of the said masses about the axis around which the roller tends to tilt is greater than the centrifugal moment of the roller carrier masses on that side of the median plane of the roller nearer to the transmission axis by an amount such that the said masses will develop a resultant centrifugal torque opposing and counterbalancing the centrifugal torque tending to tilt the roller sin a plane passing through the center of the roller and containing the transmission axis. a

7. A planetary friction transmission mechanism including two discs, a torquetransmitting planetary roller in tractive contact with said discs, a carrier for said roller, and a counterweight concentric with the roller axes, mounted on the carrier at that side of the roller more remote from the disc axis.

8. A transmission mechanism as in claim 7 in which the counterweight is a wheel capable of being rotated in an opposite direction to the roller.

9. Incombination a transmission mechanism asrin claim l with means for driving the balance wheel from the torque transmitting roller. I

10. In combination a transmission mechanism as in claim 1 with friction driving means interposed between the roller and the balance wheel for driving the latter from the former.

11. In combination, a transmission mechanism as in claim 1 in which the torque transmitting roller is ,rotatablea'round a spigot mountedon the carrier, the balance wheel being rotatable around the same axis, balls interposed between the roller and balance wheel, a ball cage stationary on the spi 0t holding the ballsvin a fixed position relative thereto and pressure means holding the roller the balls and the balance wheel in tractive frictional contact. 3

In testimony whereof I affix my signature.

' f JOHN H; HUNT.

6. In combination, a transmission gearing according to claim 1 having coaxial torus 

